1. Field of Invention
Embodiments of the present invention relate to methods and products for improving abdominal surgery. In particular, embodiments of the present invention relate to constructs comprising an allograft having at least one layer of amnion and chorion tissues for use during abdominal surgeries. The constructs are adapted for the ease of use for covering the surgical site or incisions resulting from the surgery.
2. Background of the Invention
Abdominal surgery has been used broadly for the treatment or diagnosis of diseases affecting the abdominal cavity. The surgery involves opening a region in the abdomen. Complications of abdominal surgery include, but are not limited to, bleeding, infections or inflammations (such as, chest infections, intra-abdominal infection (peritonitis), wound infection, and other infections or inflammations), post-operative paralysis of the intestine (ileus), post-operative intestinal obstruction, urinary difficulties, adhesions, hernia formation, etc. For example, string-like adhesions may occur inside the abdominal cavity, leading to blockages of the bowel, sometimes after an abdominal surgery. Additional operations are sometimes necessary to divide or remove these adhesions or to unblock the bowel.
The amnion is a thin, cellular, extraembryonic membrane that forms the inner membrane of a closed placental sac surrounding and protecting an embryo in reptiles, birds, and mammals. The sac contains the fetus and amniotic fluid or liquor amnii, in which the embryo is immersed, nourished and protected. Amnion is a tough, transparent, nerve-free, and nonvascular membrane consisting of two layers of cells: an inner, single-cell-thick layer of ectodermal epithelium and an outer covering of mesodermal, connective, and specialized smooth muscular tissue. In the later stages of pregnancy, the amnion expands to come in contact with the inner wall of the chorion creating the appearance of a thin wall of the sac extending from the margin of the placenta. The amnion and chorion are closely applied, though not fused, to one another and to the wall of the uterus. Thus, at the later stage of gestation, the fetal membranes are composed of two principal layers: the outer chorion that is in contact with maternal cells and the inner amnion that is bathed by amniotic fluid.
The amnion has multiple functions, e.g., as a covering epithelium, as an active secretary epithelium, and for intense intercellular and transcellular transport. Before or during labor, the sac breaks and the fluid drains out. Typically, the remnants of the sac membranes are observed as the white fringe lining the inner cavity of the placenta expelled after birth. The amnion can be stripped off from the placenta. The amnion has a basement membrane side and a stroma side.
The fetal membrane including amnion and chorion has been used in surgeries documented as early as 1910. See Trelford et al., 1979, Am J Obstet Gynecol, 134:833-845. Amnioplastin, an isolated and chemically processed amniotic membrane, was used for continual dural repair, peripheral nerve injuries, conjunctival graft and flexor and muscle repair. See e.g., Chao et al., 1940, The British Medical Journal, March 30. The amnion has been used for multiple medical purposes, e.g., as a graft in surgical reconstruction forming artificial vaginas or over the surgical defect of total glossectomy, as a dressing for burns, on full-thickness skin wounds or in omphalocele, and in the prevention of meningocerebral adhesions following head injury or tissue adhesion in abdominal and pelvic surgery.
In recent years, there have been renewed interests in the application of amnion in ocular surface reconstruction, for example, as an allograph for repairing corneal defects. See, for example, Tsai and Tseng, Cornea. 1994 September; 13(5):389-400; and Dua et al., Br. J. Ophthalmol 1999, 83:748-20 752. In addition, amnion and amniotic fluid have recently been used as sources of placental stem cells. See, e.g., U.S. Pat. No. 7,255,879 and WO 200073421.
Despite the clinical and published record regarding the safety and efficacy of amnion in broad surgical use, issues regarding reproducibility, safety and the precise form of amnion for each prospective indication have prevented amnion from achieving broad commercial distribution.
There is a need of improved methods and products for abdominal surgeries that would enhance wound healing, effectively reduce inflammation and inhibit fibroblast formation, scarring and adhesion formation. The present invention relates to such improved methods and products.
It is now discovered that using amnion in abdominal surgeries as described in the present invention significantly reduces inflammation and tissue adhesion, promotes uniform re-growth and epithelialization, prevents scar tissue formation, thus significantly improves performance and reduces complications of abdominal surgeries.